Electric kiln



nite States Patent Office ELECTRIC KILN Arthur H. Edgerton, Rocky River,Ohio Application February 3, 1954, Serial No. 407,859 7 Claims. (Cl.219-35) This invention relates broadly to electric kilns and morespecifically to kilns for firing vitreous enamel on small metallic partssuch asworks of art and industrial parts.

One of the objects of the'invention is to provide a transparent hood ordome defining a firing chamber for a kiln to accommodate theobservationof the work as the glaze matures therein.

Another object of the'invention is to provide a portable kiln adapted tocomplement a kit containing an assortment of tools, glazing materialsand findings.

Another object of the invention is to provide a work supporting stand orso-called trivet to facilitate the suspension of the Work in spacedrelation with the heating element while both sides of the work are beingfired.

Further objects of the invention reside in the provision of a kiln whichis light in weight, durable of structure, economical of manufacture, andefficient of operation.

Other objects and advantages more or less ancillary to the foregoing,and the manner in which all the various objects are realized, willappear in the following description, which considered in connection withthe accompanying drawings, sets forth the preferred embodiment of theinvention.

In the drawings:

Fig. l is a vertical sectional view through the improved kiln.

Fig. 2 is a plan view thereof.

Fig. 3 is a plan view of a tool for lifting the dome off the heatingunit.

Fig. 4 is a side elevational view of the work supporting stand; and

Fig. 5 is a plan view thereof.

Referring first to Fig. 1, the kiln comprises a base preferably drawnfrom sheet metal stock to form a tubular body having a concave top 11,an opening 12 therein for reception of an electric heating element 13and legs 14 in the lower open end of the body to facilitate thedissipation of heat. coil 15 of resistance wire mounted in theconventional manner in spiral groove in a plate 16 of refractorymaterial. The top of the heating element is flush with edges of the walldefining the opening 12 and the base thereof is supported on a crossbar17 welded or otherwise secured to the side wall of the base. The coil 15is coupled through lines 18 and 19 to an electrical plug 20 of usualform which is bolted to the cross bar 17 and arranged to protrudethrough an opening in the side wall of the base 10.

The work pieces may be held either by a stainless steel wire screen (notshown) laid upon the upper face of the heating element or by a stand orso-called trivet 22 adapted to rest upon the ceramic plate 16 or topplate 11 superjacent the electric coil 15. The trivet preferablycomprises a cruciform wire frame embodying a pair of base rails 24flattened in the central portions 25 thereof and welded together innormal relation to each other. The wires forming the base rails are bentvertically upwardly at equidistant points, then downwardly and inwardlyin The heating element embodies a helical gconvergent relation with thecenters 25 of the base rails 24. The height of the vertical arms isequal and the free ends of the downwardly inclined arms terminate incontigeous relation with each other slightly above the bonded center 25.

The dome 26 which forms the firing chamber of the kiln is molded as anintegral unit from clear, transparent, heatresisting glass of thecharacter sold commercially under the trade name Pyrex. The base of thedome is contoured for intimate engagement with the concave face 11 ofthe top of the kiln, and is preferably formed with bead- 27 around theouter marginal edge thereof. The dome is formed with a shouldered knob28 in the center of the top thereof anda tool such as the fork 29illustrated in Fig. 3 may be provided to'facilitate the removal of thedome after a firing operation.

In operation the work pieces arecoated with comminutecl glaze in thewell known manner, then placed upon either the screen planchet or trivet22. The dome is next placed in position on the face 11 of thetop of thekiln and the electric current turned on. As the glaze matures, theoperator may observe the characteristic changes therein; first the deepgrey or black appearance of the enamel coating, irrespective theoriginal color thereof; next the curdled effect as fusion occurs; nextthe sheen about the marginal edges of the work, and finally the shinyappearance of the entire surface of the work as the glaze reaches itsflow point. When the latter occurs, the operator may either turn off theelectric current or remove the dome and lift the trivet or planchet asthe case may be.

The glazing material melts at approximately 1500 36., and although theglass from which the dome is made softens, at a somewhat lowertemperature during the manufacture thereof, it will be recognized thatthe ambient air will prevent the dome from reaching a temperature whichwill have any deleterious effect thereon or cause any deformation orinjury thereto. Since the improved kiln affords visual inspection of thework throughout the firing operation, the craftsman may remove the piecefrom the kiln or turn off the heating element at the critical stage offusion, thus avoiding over-firing, which generally produces blackenedareas about the edges of the work, dots throughout the surface thereofwhere the glaze burns out, or irregular lumpy surface where the enamelcrawls.

Although the foregoing description is necessarily of a detailedcharacter, in order that the invention may be completely set forth, itis to be understood that the specific terminology is not intended to berestrictive or confining, and that various rearrangements of parts andmodifications of detail may be resorted to without departing from thescope or spirit of the invention as herein claimed.

What is claimed is:

1. A kiln for fusing vitreous enamels comprising a base having a discshaped top provided with a central opening, an electric heating elementin said opening capable of fusing vitreous enamels in the range of 1300F. to 1600 F. and a transparent cover composed of glass having asoftening temperature of approximately 1300 F., said cover having an endwall and a depending annular wall of a greater diameter than the heatingelement and engaging the upper surface of said top near its outer edgeand preventing free access of air to the interior of the cover, theheight of the annular wall of said cover being approximately as great asthe radius of the mouth of the cover whereby currents of air sweepingthe outer periphery of the cover will maintain solidity of the glasscover.

2. A kiln for fusing vitreous enamels comprising a base having a discshaped top provided with a central opening, a flat electric heatingelement in said opening capable of fusing vitreous enamels in the rangeof 1300 F to 1600 F. and a transparent cover composed of glass PatentedJuly 12, 1955 having a softening temperature of approximately 1300 B,said cover having an end wall and a depending annular wall of a greaterdiameter than the heating element and engaging the upper surface of saidtop near its outer edge and'preventing free access of air to theinterior of the cover, the height of the annular wall of said coverbeing approximately as great as the radius of the heating elementwhereby currents of air sweeping the outer periphery of the cover willmaintain solidity of the glass cover.

3. A kiln for fusing vitreous enamels comprising a base having a discshaped top provided with a central opening, an electric heating elementin said opening capable of fusing vitreous enamels in the range of 1300to 1600" F. and a transparent cover composed of glass having a softeningtemperature of approximately 1300 F., said cover having an end Walland-a depending annular wall of a greater diameter than the heatingelement and engaging the upper surface of said top near its outer edgeand preventing free access of air to the interior of the cover, theheight of the annular wall of said cover being approximately as great asthe radius of the mouth of the cover whereby currents of air sweepingthe outer periphery of the cover will maintain solidity of the glasscover and whereby the vitrifaction of vitreous enamels melting from 1300F. to 1600 F. may be observed during the heating operation and removedfrom the kiln by lifting the cover therefrom when the vitreous enamelsattain a shiny smooth appearance.

4. A kiln of the type as set forth in claim 1 including a marginal rimportion on said disc shaped top of a height greater than the centralportion of the top for properly positioning said cover thereon.

5. A kiln of the type as defined in and by claim 1 including a workholder removably supported on said heating element.

6. A kiln of the type as defined in and by claim 1 including liftingmeans detachably connected to said cover for the removal thereof fromthe kiln.

7, A kiln of the type as defined in and by claim 1 including heatinsulating means in said base of the kiln.

References (Iited in the file of this patent UNITED STATES PATENTS

